写一个if then else类型语句的简洁方法

Question

Let's say I have a criteria and I want to add a delta if that criteria is true, and do the opposite (subtract) if it is false.

bool bBoolean;
int iDelta;
int iQuantity;

Is there a more concise and elegant way to write that piece of code ? I mean without repeating the keywords iQuantity and iDelta.

if(bBoolean)
  iQuantity -= iDelta;
else 
  iQuantity += iDelta;

Answer 1

The shortest thing I can think of is:

iQuantity += (bBoolean) ? -iDelta : iDelta;

Edit: This is commonly called a ternary statement, though it's proper name (what it's called in the standard) is "conditional expression" or "conditional operator".

(Thanks to Rune for the official name.)

Answer 2

This is the ternary operator. It is frowned upon by some for its potential to be less clear than if...else . I like it, but try to be careful.

int sign = criteria ? -1 : 1;
quantity += (delta * sign);

Answer 3

iQuantity += (1-2*bBoolean)*iDelta;

在某些处理器上，额外算法比分支更快。

Answer 4

Why not:

int tmpDelta = iDelta;
if (iBoolean)
{
  tmpDelta = -tmpDelta;
}
iQuantity += tmpDelta;

To me, when I write or read code, I prefer to have something that as straight-forward as possible. This says that the code will always update iQuantity , and that the update will be inversed if iBoolean is true.

Edit: Updated not to modify iDelta .